As time went on, cannon, though primitively formed as described, increased in size that prodigious balls might be expelled from them against walled places, in imitation of the ancient machine which they had superseded; thus they soon became of enormous bore, until they attained the dignity of bombardes, like Mons Meg in Edinburgh Castle; but the difficulty of managing these pieces, and the growing knowledge that iron shot of much less weight could be impelled further by the use of better powder, gradually introduced the cast metal cannon used at the present day. The five little cannon used at Cressi, to the wonder of the French who had _none_, were doubtless the same that Edward used at the siege of Calais in the following year. In 1366 the Venetians, when besieging a town now named Chioggia in Lombardy, had with them two small pieces of artillery having leaden balls, worked by Germans, according to Le Blond's "Elements of War," dedicated to Louis of Lorraine; and battering guns were used by the Turks against the Christians at Constantinople in 1394; but the great bombardes were at their zenith when, in 1451, Mahomet II. began his march against the same city, with fourteen gigantic guns, which threw stone shot seventy-eight inches in circumference, weighing 800 lbs. In the siege, traces of which remain to this day, the Christians are supposed to have been without cannon, as they omitted to demolish the great bridge of boats which was constructed by the Turks and conduced so much to the reduction of the city. For more than four centuries the guns of Mahomet II. protected the Dardanelles--the gate of the Eastern Empire; and, as an old traveller relates, that as they were shotted when fired on holidays, land was usually to be had very cheap on the opposite side of the straits. Though practically these great pieces of artillery have given place to Krupp and other guns, they still remain on their old sites; but cannon of this description can only be discharged with effect when the object passes their line of fire, as they are not mounted on carriages but built into a wall. Some of those at the Dardanelles carry balls 26½ inches in diameter, and lie flat on a paved terrace near the level of the water, where they opened on our fleet in 1808, when Admiral Sir John Duckworth forced the passage of the Straits. By a granite shot from one of these, when the fleet returned, _H.M.S. Royal George_ had her whole cutwater carried away; by another, the mainmast of the Windsor Castle was cut in two like a fishing-rod; another carried away the wheel of the _Repulse_, at the same moment killing and wounding twenty-four men, and rendering the ship so unmanageable, that but for the noble seamanship of her crew, she must have gone on shore.